Sonic generators used to convert electrical energy into acoustic and kinetic energy for transmission to fluid mediums are known. Such devices are illustrated, for example, in U.K. Patent Specification 2,152,728 to Bodine and U.S. Pat. No. 2,468,515 to Robinson.
The sonic generators there disclosed, however, suffer disadvantages. The apparatus taught by Bodine in the aforementioned U.K. patent utilizes orboresonant drives similar to the types described in Bodine's U.S. Pat. Nos. 3,633,877, 3,684,037, 3,360,056 and 4,265,129. These drives limit the upper range of frequencies such units can transmit to a fluid medium. Since the transmission of acoustic power between the resonant bar and the fluid is less efficient at lower frequencies, this limitation lowers the acoustic efficiency of the Bodine apparatus. Further, Bodine necessarily utilizes a coupling between this orbiting mass oscillators and his resonant bar which attempts to isolate the inertial forces of the vibrating bar from the motor. Without such coupling, the magnitude of these forces are sufficient to cause relatively rapid failure of the orbiting mass oscillator drive motors, be they hydraulic or electric. Bodine further exposes a large force on a relatively small member used to support the resonant bar with the result, again, that failure of the apparatus is increased. Because of the high forces imposed upon the motors and the insufficient support provided in the Bodine design, premature failure of the unit is likely.
U.S. Pat. No. 2,468,515 to Robinson teaches restraining a resonating bar with steel bushings at respectively oppositely located end portions of the bar. Such supports cause energy to be lost through the support structure which energy would be better utilized in the fluid medium. Further and because of the mounting, Robinson's structure has a very high stress concentration both at the support point and at the point of maximum bending stress. Such stress concentration can eventually cause unnecessary damage to the resonant member and/or premature failure and limit the mechanical stresses that can be sustained without failure. Yet a further disadvantage of the Robinson apparatus is that he utilizes a two dimensional movement of his resonant bar. Such a design causes the pressure to radiate outwardly into the fluid medium in a single plane whereas with a three dimensional movement of the resonant bar, pressure will radiate outwardly from the bar in all directions.